This invention pertains to dot matrix type printing and, more particularly, to dot matrix type printers employing thermal print heads.
At present there are available thermal print heads which are used in dot matrix printing. These print heads comprise effectively miniature resistors which when fed a pulse of current generate enough heat to melt a portion of the ribbon opposite the element. The melted portion is transferred by contact to a record medium such as paper immediately opposite the ribbon. This type of head has several limitations. The main limitation is that the printing rate is slower than some other types of printers because of the thermal inertia. In order to enhance the print rate, people have generally applied very large current pulses to the resistors. However, the use of large current pulses introduces thermal and electrical shocks into the head structure, shortening its life.